Unless you fill to the top, we need to be sure whether we refer to water depth or to pond depth.Mine pond is 5 1/2 feet and I get about 5 feet of water depth. Personally, I think that 3 feet is a bit shallow, and 4 - 5 feet of water would be ok for a small pond of about 2000 - 2500 imp gallons.Bigger Koi ? ... you will need a bigger pond than mine.Mine is gravity fed, and the water pump is in the filter, so my electricity bill will depend on my turnover rate which is in turn determined by my selection of pump.Seeing my koi ? ... With my set up, which includes a WaterCo, I can see every stone on the bottom, and my koi are also quite friendly because of the small size of the pond, as well as their having spent 4 - 6 months in a F/G quarantine tank. They come to the surface and sometimes even splash me when I appear late with their feed.My pond is raised 2 feet above ground and 3 1/2 feet underneath. Yes, kids can hurt themselves, but they will have to try quite hard. :-D

Nearly forgot - you will be putting quite a few tons of weight on the ground. Even though this would be alright in an open area, do remember to check if you are going to locate your pond anywhere near the house.

As for the effect of depth on your koi, I do not have any scientific evidence beyond my belief that the different water pressure, as well as the provision of some security / refuge may have a positive effect on your fish.

Our " other half " all seem to be the same. My first pond was a result of this, and also because the architect friend wanted to " produce a rustic appearance ".

My dogs went in for a swim every few days, monitor lizards and frogs also had a great time, frog eggs everywhere, and I nearly drowned when I got home after ( those days ) Happy Hours ! The wind also brought in all kinds of debris, and you will need a skimmer if you want to preserve the water. Yes, my profile shows my second attempt after I learned my lesson with regards to basic koi keeping.

Yes, I use the WaterCo in addition to a gravity fed system consisting of 2 Vortex and a settlement chamber.

My children were young then, and having their friends over was quire common. All it took was for me to say that I was very worried if my dogs accidentally pushed some of them into the pond - ZAAAAP !!! - raised pond :-)) :-)) :-))

Remember that if you want a gravity fed filter system*, you will also need to recess the filters into the ground. In the case of your pond design, this could be quite complicated because you will need a whole bunch of underground pipes.

* where all other variables are the same, a gravity fed system will likely give you the best water clarity. Not mandatory however - you can compensate in many ways if you decide on the conventional pump fed system.

All the best, I am going to try my best this morning to return my sparkling new TV which I specifically bought to watch Malaysia win the Thomas Cup. :-D :-D :-D

Just to contribute my two cents on the raised up pond wall. When I started this hobby 4 yrs ago, my koi pond was constructed that it was flat on the ground (no pond wall) for aesthetic reason. Later on I ran into a few problems: (i) dirt (dust, dried leaves, etc.) always ended up on the surface of the pond when there was a gust (ii) fish appeared to be scared (bcos human appeared very big when approaching the pond) (iii) netting koi was a bigger challenge (no support from pond wall). I reconstructed my koi 2 yrs ago by raising up pond wall by 1.5ft. All the problems solved. Now I can even sit on the raised up portion to enjoy viewing my koi.

On your HM's objection, try harder and I believe there's way to convince her ... ask koi kichis in this forum and they will tell you how :-D

There was once a time where deep ponds were thought to be a factor towards causing sinking disease. How true this is I'm not sure, but IMHO not too deep, about 4 - 5feet is good I think, both for the koi's and for our own maintenance ease. :-D

Be updated in the world of koi. Jangankan seperti "Koi di bawah bottom drain"

Raised up pond wall confirmed not going to happen. Perhaps during another renovation in the future, but definitely not this round.

On the bright side the main contractor has agreed to deepen the pond to 1.5m or 5 feet for a small fee which is no way close to a diamond ring, LV handbag or a baby. Btw HM is fairly interested in the Koi pond as well.

IMHO, hobbyist pond depth best to be build between 4 feet to max 5.5 feet. Reason, unlike koi dealers who separate tosai for shallow pond and jumbo's in deeper pond of above 6 feet, we hobbyist mix all range of kois from tosai till whatever 'sai' in one pond. I heard cases whereby tosai which kept in deep pond tend to get sinking disease (imagine the pressure at that depth). And on top of that all the security measure Capt highlighted earlier.

I had put grill's surrounding my 5feet depth pond to safe guard my kids, and the visitors. I still able to go in the pond with full water to check things out if anything goes wrong. :)